Numerous types of resonant structures, often used in electromagnetic filters, are known in the prior art. For most applications, a conductor and/or dielectric material must be held in a fixed position with respect to a wall, such as the cavity wall of a filter housing. In some resonant structures, conductors are held between slabs of dielectric material which are forced together using screws, springs or adhesive. In many applications, however, it is desirable that a resonator have little physical contact with other objects. Small screws or bolts may be placed through an opening in a resonator such as a dielectric puck, in order to attach the resonator to another structure with minimal physical contact. Although some degradation in performance of the resonator may undoubtedly be attributed to such mounting structures, that degradation is generally small in comparison to other losses which affect the overall quality of the resonator.
The introduction of superconducting materials into resonant structures has significantly decreased the surface resistance of those structures, thereby raising the quality factor "Q" of the filtering devices utilizing the resonant structures. Losses due to mounting, which were previously insignificant, have now become an important limiting factor in the quality of a filter. Prior structures, such as providing a threaded opening or the like in a resonator, may no longer be desirable, because they interfere with the electromagnetic fields at the surface of the resonator. In general, the greater the size of a mounting mechanism or the more contact it has with the resonator, the more likely it will interfere with the electromagnetic properties of the resonator or resonant cavity in which it is used. The desire for reduced size in mounting mechanisms is at odds with the need to hold the resonator at a precise location with minimal chance for mounting failure. In the case of filters using superconductors, the structural demands on the mounting mechanism are increased, since that mechanism will be subjected to temperatures ranging from room temperature to hundreds of degrees below 0.degree. C.
In U.S. Pat. No. 5,604,472, the disclosure of which is incorporated herein by reference, the assignee of the present application used a resonator mounting device having a stand with a groove in the head of the stand surrounded by two wings. A cap with a groove and two wings fit over the head and was attached to the stand by rings. While such a device operates satisfactorily, assembly of the rings onto the wings can be difficult. In certain positions of the stand, it might also be cumbersome to hold the cap to the stand while the rings were applied. In addition, tolerances of the grooves had to be relatively precise or the cap would not hold the resonator to the stand in a fixed position. It is also possible for the resonator to vary in cross-section, resulting in the rings fitting too tightly for assembly or too loosely to clamp effectively once assembled.